[Pharmwaste] Sunlight breaks down antiepileptic drug

[Tenace, Laurie]

http://pubs.acs.org/subscribe/journals/esthag/40/i19/pdf/100106news.pdf
(scroll to second page)

Sunlight breaks down antiepileptic drug

When researchers first looked for
pharmaceuticals in the environment
in Europe and elsewhere,
some of the highest concentrations
they found were for residues of the
antiepileptic drug carbamazepine,
which showed up in a variety of
places, including drinking-water
treatment plants and sewage effluent.
The drug, which is sold as
Tegretol and under other commercial
names, treats seizures as well
as bipolar disorder. New research
published in this issue of ES&T (pp
5977-5983) shows that when carbamazepine
is exposed to sunlight
in an estuary-like setting, it breaks
down into a more toxic compound,
acridine.
Carbamazepine's structure-
three rings of carbon with an
amine attached-makes it susceptible
to fracturing under certain
conditions. That quality led
researchers to target the drug for
further study with regard to its
photochemistry. Previous research
has shown that in the presence of
hydrogen peroxide and UV light,
carbamazepine breaks down to
acridine, which is both mutagenic
and carcinogenic (Chemosphere
2004, 54, 497-505).
Although obtaining information
about carbamazepine's use
is difficult, the drug's widespread
consumption is reflected in its
high concentrations in the environment.
It has been found at levels
up to several micrograms per liter
in sewage treatment plants, first
measured by Thomas Ternes of the
Federal Institute of Hydrology (Germany)
in 1998 (Water Res. 1998,
32, 3245-3260). Scientists at the
U.S. Geological Survey later measured
it at parts-per-billion levels in
U.S. streams (Environ. Sci. Technol.
2005, 39, 193A-194A), and researchers
from Environment Canada
recently added to those North
American data (Environ. Toxicol.
Chem. 2006, 25, 2163-2176).
A team of researchers led by
Serge Chiron at the University of
Provence (France) has now taken
a closer look at the photodegradation
of carbamazepine. They created
a laboratory setting to mimic
the natural estuary waters of the
Rhône delta in southern France. By
adding humic acids, Fe(III), and
nitrate to tap water, they created
"artificial" river water.
The researchers then subjected
carbamazepine to irradiation experiments
that simulated natural
light with a mercury lamp emitting
at UV and visible wavelengths.
They documented the resulting
photodegradation of the drug into
a dozen intermediate forms, paying
particular attention to its behavior
in the presence of chlorine.
Among the breakdown products,
the researchers detected acridine,
which occurred as the 4th of
12 intermediates. The compound
is relatively stable, and after 8 h, its
concentrations accounted for 10%
of the carbamazepine in the initial
samples. The final three degradation
products were chlorinated.
The study "reinforces the idea
that photochemistry transforms
compounds [and] doesn't completely
destroy them," says Kristopher
McNeill of the University
of Minnesota, but it "sometimes
turns them into other organic contaminants,
sometimes more toxic
than the original."
Researchers comment that the
results cannot be scaled up to estimate
the amount of the potential
mutagen produced in the environment.
"Both the light source and
the carbamazepine levels were
very different than they would be
in the natural environment," says
Mihaela Stefan, a research scientist
at Trojan Technologies (Canada).
News Briefs
Conservation and
desalination
Desalination is an extremely costly
way to produce drinking water, according
to an analysis by the Pacific
Institute, a nonpartisan think tank.
In Desalination, With a Grain of Salt,
the institute contends that most of
California's current desalination projects
fail to address economic realities
and environmental concerns.
Electricity accounts for 44% of the
typical costs of producing drinking
water with plants that use reverse
osmosis. An energy rate hike of 25%
pushes up water prices by 11%. Also,
desalination can have environmental
consequences. The discharge of
the highly salty waste brine-often
laced with chemicals and metals-
can harm fish populations and accumulate
in the food chain, the report
points out.
India bans soft drinks
Multiple news agencies have reported
that Coke and Pepsi products
have been removed from supermarket
shelves in some states in India
after a New Delhi-based group reported
high levels of pesticides in
the soft drinks. The Centre for Science
and Environment tested 57
samples of Coca-Cola and
PepsiCo
soft drinks from
25 manufacturing plants
throughout India. In the
study, the center found 3-5
different pesticides in each
sample at levels 24× higher
than the national norms.
For instance, one bottle of Coca-Cola
contained the pesticide lindane at
levels 140× the national standards.
This latest report builds on earlier
research conducted by the center
in 2003. The Indian national government
continues to debate enacting
regulations.
RHONDA SAUNDERS
october 1, 2006 / Environmental Science & Te chnology n 5827
Environmental t News
She points out that the experiments
had much higher concentrations
of the drug than those
reported for natural waters and
used a different spectral distribution
and intensity of UV light than
what is present in natural sunlight.
The work "still is a bench-scale
kind of experimental system," says
Linking atmospheric mercury to fish advisories
~4× more, according to Orihel.
The researchers found that after
8 weeks, <1% of the isotopeenriched
mercury was converted
to methylmercury, while a much
higher percentage was reemitted
to the atmosphere. However, Orihel
emphasizes that even a small
percentage of methylmercury is
harmful. "It may be a tiny amount,
but that is all it takes to drive those
fish advisories," she says.
James Hurley, an aquatic chemist
with the University of Wisconsin
Sea Grant Institute, says the study
shows that decreasing atmospheric
loading should lower methylmercury
production and, presumably,
bioaccumulation in fish.
And Hammerschmidt adds
that his own studies bolster this
conclusion. In Alaskan lakes, he
and colleagues measured loadings
of inorganic mercury and
the flux of methylmercury out of
the sediments. The relationship
is linear, he reported in August at
the Eighth International Conference
on Mercury as a Global Pollutant.
Last year, Hammerschmidt
found a similar relationship between
methylmercury in mosquitoes
and average deposition rates
of mercury in U.S. lakes (Environ.
Sci. Technol. 2005, 39,
3034-3039).
At the August meeting,
Orihel reported the
same linear relationship
for small fish. Her
team found that isotope-
labeled mercury
accounted for up to a
third of the total concentration
of mercury
in the muscle tissues
of young trout living in
the lake mesocosms.
High methylmercury
concentrations
in North American
freshwater fish have
prompted health authorities
in Canada and
most U.S. states to warn against
eating too much of the fish. Coaland
oil-fired power plants are the
largest sources of mercury emissions
in the U.S., according to the
U.S. EPA.
But emissions controls are controversial,
in part because of the
complexity of the mercury cycle.
In March 2005, EPA adopted a capand-
trade rule, which aims to reduce
mercury emissions 21% by
2010 and 69% by 2018. The new
study suggests that limits could
achieve their intended outcomes
rather quickly.
-REBECCA RENNER
Chris Metcalfe of Trent University
(Canada). "The next step would be
obviously to look at it in natural
conditions."
Real estuarine environments
with iron, dissolved organic matter,
and other materials that promote
photodegradation would also
have chlorine present. "Generally
speaking, chlorinated compounds
are more toxic than nonchlorinated
ones, and chlorination potentially
contributes to greater
bioaccumulation," McNeill says.
He agrees with the authors that
further studies of the chlorinated
forms are necessary.
-NAOMI LUBICK

Laurie J. Tenace
Environmental Specialist
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us  
 
view our mercury web pages at: 
http://www.dep.state.fl.us/waste/categories/mercury/default.htm 

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